Rapid assessment of perfect time for transferring wells to water injection for pressure maintenance in low-permeable sediments of Tyumen suite of LLC «RN-Uvatneftegas» oilfields

A significant part of the initial geological reserves of LLC “RN-Uvatneftegas” oilfields are concentrated in deposits with abnormally low reservoir properties (porosity, permeability). The organization strategy of pressure maintenance of such oilfields significantly affect to the economic profitability of the reservoir development. One of the major tasks to achieve this goal is to determine the perfect time for application injection wells in oil production before forming the pressure maintenance system. Often, the solution to this issue turns out to be labor-intensive. In this regard, the analytical tool has been developed that allows rapidly assess the perfect time for transferring wells to water injection for pressure maintenance forming. The developed tool is based on a statistical analysis of the decline rate of horizontal wells fluid rates at the RN-Uvatneftegas oilfields. And also a comparative analysis of the results of the developed tool and other existing methods was carried out. The analysis showed that the developed tool is distinguished by its accuracy, simplicity and efficiency of work.

Denitrification of Permeable Sand Sediment in a Headwater River Is Mainly Influenced by Water Chemistry, Rather Than Sediment Particle Size and Heterogeneity

Sediment particle size and heterogeneity play an important role in sediment denitrification through direct and indirect effects on, for example, the material exchange rate, environmental gradients, microbial biomass, and grazing pressure. However, these effects have mostly been observed in impermeable sediments. On the other hand, the material exchange of permeable sediments is dominated by advection instead of diffusion, with the exchange or transport rates exceeding those of diffusion by two orders of magnitude relative to impermeable sediments. The impact of permeable sediment particle size and heterogeneity on denitrification remains poorly understood, especially at the millimeter scale. Here, we conducted an in situ control experiment in which we sorted sand sediment into four homogeneous-particle-sizes treatments and four heterogeneous treatments. Each treatment was deployed, in replicate, within the riffle in three different river reaches with contrasting physicochemical characteristics. After incubating for three months, sediment denitrifier communities (nirS, nirK, nosZ), denitrification gene abundances (nirS, nirK, nosZ), and denitrification rates in all treatments were measured. We found that most of the denitrifying microbes in permeable sediments were unclassified denitrifying microbes, and particle size and heterogeneity were not significantly correlated with the functional gene abundances or denitrification rates. Water chemistry was the key controlling factor for the denitrification of permeable sediments. Water NO3−-N directly regulated the denitrification rate of permeable sediments, instead of indirectly regulating the denitrification rate of sediments by affecting the chemical characteristics of the sediments. Our study fills a knowledge gap of denitrification in permeable sediment in a headwater river and highlights that particle size and heterogeneity are less important for permeable sediment denitrification.

REY Patterns and Their Natural Anomalies in Waters and Brines: The Correlation of Gd and Y Anomalies

Rare earths and yttrium (REY) distribution patterns of the hydrosphere reveal systematic correlations of Gd and Y anomalies besides the non-correlated redox-dependent Ce and Eu anomalies. Eu anomalies are inherited by dissolution of feldspars in igneous rocks, whereas Ce, Gd and Y anomalies develop in aqueous systems in contact with minerals and amorphous matter. Natural, positive Gd and Y anomalies in REY patterns characterize high-salinity fluids from the Dead Sea, Israel/Jordan, the Great Salt Lake, USA, the Aral Sea, Kazakhstan/Uzbekistan, ground- and surface water worldwide. Extreme Gd anomalies mostly originate from anthropogenic sources. The correlation of Gd and Y anomalies at low temperature in water bodies differ from geothermal ones. In nature, dynamic systems prevail in which either solids settle in water columns or water moves through permeable sediments or sedimentary rocks. In both cases, the anomalies in water develop due to repeated equilibration with solid matter. Thus, these anomalies provide information about the hydrological history of seawater, fresh groundwater and continental brines. When migrating, the interaction of aqueous phases with mineral surfaces leads to increasing anomalies because the more hydrophillic Gd and Y preferentially remain in the aqueous phase compared to their nearest neighbors. The correlation coefficients between Gd and Y anomalies in groundwater is 0.5–0.9. In lakes and oceans, it is about 0.1–0.8, under anomalous conditions it can increase to 1.

Non-Dispersive Anti-Washout Grout Design Based on Geotechnical Experimentation for Application in Subsidence-Prone Underwater Karstic Formations

A new non-dispersive, anti-washout grout consisting of ordinary Portland cement, slag, superplasticizer, and methylbenzyl cellulose is proposed herein for the treatment of open karst, jointed and fractured rock, open-work gravel, and permeable sediments. A series of laboratory experiments were performed to design an anti-wash out grout suitable for grout injection of coarse aggregates depicting partially and open-jointed saturated rock mass and grouting concrete aggregates for underwater construction. The Taguchi orthogonal array was used to obtain nine different grout mix ratios. A total of four variables were considered, each with three different levels of the water–cement ratio, slag, and dosage of additives such as the superplasticizer and methyl benzyl cellulose. The laboratory determination of grout characteristics recording of mini slump, temperature, pH, visual assessment of grout dispersion, bleeding, and initial setting time and as well as uniaxial compressive strengths and permeabilities of the hardened grout samples were tested. To evaluate the suitability of the grout mixes, an analysis of variance was used for factor analysis and Grey relational analysis (GRA) was used to determine the optimal grout mix design. Based on the GRA, the following levels of the factors afforded the best results: water level 1 (0.3%), SP level 3 (0.01%), methylbenzyl cellulose level 2 (0.002%), and slag level 3 (0.1%). This paper describes the research methodology, detailed research observations, and analyses involved in designing the appropriate concrete mix. Based on the conclusions, relevant commendations regarding the suitability of grout testing equipment and grout mix designs are presented.

The impact of sediment resuspension on non-cyanobacterial nitrogen fixation along the Southern Baltic coastline

<p>Benthic nitrogen fixation by heterotrophic non-cyanobacterial diazotrophs (NCDs) is common in anoxic marine sediments, however, it is currently unclear how resuspension of sediments affects this activity. Moreover, physical mixing processes are strongest in shallow coastal waters where permeable sediments prevail and anoxic conditions rarely occur. It is therefore of interest to understand whether such coastal sites provide ecological niches for NCDs. In order to gain insight into NCD nitrogen fixation during sediment resuspension, slurry incubations were carried out with nearshore sediments from stations along the Southern Baltic coastline and, for comparison, with anoxic sediments from the Gdansk Deep. Parallel to this, we carried out separate incubations treated with sodium molybdate, an inhibitor of sulfate reducing bacteria (SRB), to differentiate SRB activity from total NCD activity. Our data show low rates of nitrogen fixation by NCDs and indicate that SRBs (e.g. <em>Desulfovibro</em>) are actively fixing nitrogen. Nitrogen fixation rates varied greatly between locations, influenced by sediment grain size and POC-loading. Interestingly, nitrogen fixation took place despite of micromolar concentrations of inorganic nitrogen, which implies that NCDs may be more resilient towards N-stress than formerly expected. In conclusion, our experimental study supports previous findings of stimulation of nitrogen fixation by sediment resuspension, even in permeable sediments, however, at low rates.</p>

QUANTITATIVE ASSESSMENT OF GROUNDWATER PROTECTION IN THE ZONE OF INFLUENCED OF THE GOMEL CHEMICAL PLANT

The formation of dumps from the production of phosphorous fertilizers at the JSC "Gomel Chemical Plant" is a significant factor affecting the geological environment, which leads primarily to contamination of soil and ground-water. The insignificant thickness of the aeration zone (0.5 to 5.0 m), the absence of low permeable layers in its section, and the downward aquifer recharge make it possible for sulfate, phosphate, and ammonium migrant components to enter groundwater from the surface. Based on the analysis of actual geological and hydrogeological data, a quantitative assessment of the protection of pressure water within the zone influenced by JSC "Gomel Chemical Plant" was given. It is established that their protection depends on the thickness of low permeable sediments, their material composition, and the ratio of aquifer levels. The time of migration of pollutants between groundwater and pressure water was determined. Categories of groundwater protection were identified and their territorial differentiation was established. The protective properties of low permeable sediments were evaluated, taking into account their potential to reduce groundwater contamination with sulfates, phosphates, and ammonium. It was found that the moraine deposits of the first low permeable layer most effectively reduce phosphate and ammonium contamination, while not interfering with the migration of sulfate ions. The second low permeable layer, represented by siltstones, leads to a significant reduction in the flow of pollutants into the Paleogene aquifer. Analysis of the dynamics of sulfate ion concentrations was given, which generally indicated a downward trend in the studied aquifers.

GIS-Based Groundwater Potentiality Mapping Using AHP and FR Models in Central Antalya, Turkey

Groundwater is considered one of the essential natural resources stored beneath the earth's surface by infiltration through various rock layers. Groundwater potential supplies almost 30% of fresh water globally, and in general, 65% of groundwater is used for agricultural irrigation, 25% as drinking water, and the remaining 10% is utilized as industrial water. This study aimed to delineate potential groundwater zones in the central Antalya province, Turkey, using the analytical hierarchy process (AHP) and frequency ratio (FR). Seven thematic layers, including lithology, slope, drainage density, landcover/land use, lineament density, rainfall, and soil depth, were considered as influencing factors for these models. The preparation of all geospatial datasets was carried out in the GIS environment and Google Earth Engine. Additionally, some authorized relevant web portals were also tried for obtaining the required spatial data. The findings of analysis by AHP and FR models showed that Muratpasa, Kepez, and eastern Dosemealti in the eastern part of the study area are characterized by a high potentiality of groundwater. In contrast, the regions in the southern and the western parts covered by igneous rocks and other less permeable sediments, also featuring high and steep slopes, were also followed by a low or very low groundwater potential. Consequently, the results from both models were assessed using the receiver operating curve (ROC) and area under the curve (AUC) for validation. The validation in this study confirmed the higher effectivity of the results achieved by FR than the AHP model.

Variable Seepage Meter Efficiency in High-Permeability Settings

The efficiency of seepage meters, long considered a fixed property associated with the meter design, is not constant in highly permeable sediments. Instead, efficiency varies substantially with seepage bag fullness, duration of bag attachment, depth of meter insertion into the sediments, and seepage velocity. Tests conducted in a seepage test tank filled with isotropic sand with a hydraulic conductivity of about 60 m/d indicate that seepage meter efficiency varies widely and decreases unpredictably when the volume of the seepage bag is greater than about 65 to 70 percent full or less than about 15 to 20 percent full. Seepage generally decreases with duration of bag attachment even when operated in the mid-range of bag fullness. Stopping flow through the seepage meter during bag attachment or removal also results in a decrease in meter efficiency. Numerical modeling indicates efficiency is inversely related to hydraulic conductivity in highly permeable sediments. An efficiency close to 1 for a meter installed in sediment with a hydraulic conductivity of 1 m/d decreases to about 60 and then 10 percent when hydraulic conductivity is increased to 10 and 100 m/d, respectively. These large efficiency reductions apply only to high-permeability settings, such as wave- or tidally washed coarse sand or gravel, or fluvial settings with an actively mobile sand or gravel bed, where low resistance to flow through the porous media allows bypass flow around the seepage cylinder to readily occur. In more typical settings, much greater resistance to bypass flow suppresses small changes in meter resistance during inflation or deflation of seepage bags.

Spatial variations in sedimentary N-transformation rates in the North Sea (German Bight)

In this study, we investigate the role of sedimentary N cycling in the southern North Sea. We present a budget of ammonification, nitrification and sedimentary NO3- consumption and denitrification in contrasting sediment types of the German Bight (southern North Sea), including novel net ammonification rates. We incubated sediment cores from four representative locations in the German Bight (permeable, semi-permeable and impermeable sediments) with labeled nitrate and ammonium to calculate benthic fluxes of nitrate and ammonium and gross rates of ammonification and nitrification. Ammonium fluxes generally suggest oxic degradation of organic matter, but elevated fluxes at one sampling site point towards the importance of bioirrigation or short-term accumulation of organic matter. Sedimentary fluxes of dissolved inorganic nitrogen are an important source for primary producers in the water column, supporting ∼7 % to 59 % of the average annual primary production, depending on water depth. We find that ammonification and oxygen penetration depth are the main drivers of sedimentary nitrification, but this nitrification is closely linked to denitrification. One-third of freshly produced nitrate in impermeable sediment and two-thirds in permeable sediment were reduced to N2. The semi-permeable and permeable sediments are responsible for ∼68 % of the total benthic N2 production rates, which, based solely on our data, amounts to ∼1030 t N d−1 in the southern North Sea. Thus, we conclude that semi-permeable and permeable sediments are the main sinks of reactive N, counteracting eutrophication in the southern North Sea (German Bight).